Placeholder Image

字幕表 動画を再生する

審査済み この字幕は審査済みです
  • ["An inefficient virus kills its host. A clever virus stays with it." - James Lovelock]

    ["非効率なウィルスは宿主を殺す。賢いウィルスは宿主と一緒にいる。" - ジェームズ・ラヴロック]

  • It's spring 2021, the Alpha variant of the coronavirus has spread rapidly, becoming the dominant variant worldwide.


  • But another more transmissible variant is about to appearDelta.


  • What happens when two variants clash?


  • Let's do a thought experiment.


  • Suppose that the variants reach a hypothetical isolated city of 1 million people who are completely susceptible to both viruses on the same day.


  • When a person here is infected with Alpha, they transmit it to, on average, 5 close contacts,


  • then, begin to feel sick and immediately isolate themselves for the rest of the simulation.


  • The same thing happens with Delta, except that an infected person transmits it to, on average, 7.5 close contacts.


  • What would you guess happens next?


  • After six days, Alpha will have infected 15,625 people; Delta will have infected more than 10 times as many.


  • Just 20 hours later, Delta will have infected the rest of the population, all before Alpha could infect 6% of it.


  • With no one left to infect, Alpha dies out.


  • This model is drastically simplified, but it accurately reflects one thing that did happen in real life:


  • When both variants competed, Delta drove Alpha towards extinction in a matter of weeks.


  • Viruses are wildly successful organisms.


  • There are about 100 million times as many virus particles on Earth as there are stars in the observable universe.


  • Even so, viruses can and do go extinct.


  • There are three main ways that can happen.


  • First, a virus could run out of hosts.


  • This might have happened in early 2020 to a flu lineage known as B/Yamagata.

    これは、2020 年初頭に B/Yamagata と呼ばれるインフルエンザの系統に起こった可能性があります。

  • When much of the world shut down, social-distanced, and wore masks to slow the spread of COVID-19,

    COVID-19 の拡散を遅らせるために、世界の多くが閉鎖され、ソーシャルディスタンスを実践し、マスクを着用したとき、

  • that dramatically reduced the number of hosts available for B/Yamagata to infect.

    その結果、B/Yamagata が感染できる宿主の数が劇的に減少したのです。

  • It'll take a few more flu seasons to know for sure if it's truly extinct or just hiding out in an animal reservoir.


  • Many viruses, as part of their life cycle, cause diseases severe enough to kill their hosts.


  • This can be a problem because if a virus kills all its hosts, it could, in theory, run out of hosts to infect and go extinct.


  • This almost happened back in 1950s Australia.


  • At the time, Australia was overrun by the European rabbit, an invasive species.


  • So, in an attempt to control the population, scientists released a virus called myxoma, which had been previously shown to be almost 100% lethal to European rabbits.


  • During the initial outbreak, as planned, tens, perhaps hundreds, of millions of European rabbits died.


  • But as the virus spread, it evolved a series of mutations that happened to make it less deadly, killing rabbits more slowly and killing fewer rabbits overall.


  • With more infected hosts hopping around, this strain of the virus was more likely to spread than its deadlier cousin.


  • And, of course, rabbits evolved, too, to mount better immune responses.


  • Overall, instead of killing every single rabbit, the virus evolved, the rabbit population bounced back, and both survived.


  • The second way a virus could go extinct is if humans fight back with an effective vaccine and win.


  • Vaccination campaigns have driven two viruses essentially to extinction since vaccines were invented in the 1800s: smallpox and rinderpest, which kills cattle.


  • More on vaccination later.


  • The third way a virus can go extinct is if it's outcompeted by another virus or strain, like we saw earlier with Delta and Alpha.


  • By the way, viruses don't always compete with each other.


  • A viral species can carve out its own distinct niche, for example, influenza infects your respiratory tract, and norovirus infects cells in your intestine, so both of these viruses can co-exist.


  • A virus' ecological niche can be tiny.


  • Hepatitis B and Hepatitis C viruses can infect the same cell; Hep B occupies the nucleus and Hep C occupies the cytoplasm.


  • In fact, epidemiologists estimate that 2 to 10 percent of people with Hep C are also infected with Hep B.


  • So, will SARS-CoV-2, the species of virus that causes COVID-19, ever go extinct?

    では、COVID-19 の原因ウイルスである SARS-CoV-2 は絶滅することはないのでしょうか?

  • Variants within the species will continue to arise.


  • Those variants might drive prior ones to extinctionor not.


  • Regardless of how the variants competeor don't, the species itself, to which all the variants belong, is pretty firmly established among humans.


  • If we managed to vaccinate enough people, could we drive SARS-CoV-2 to extinction?

    もし、十分な数のワクチンを接種することができれば、SARS-CoV-2 を絶滅に追いやることができるのでしょうか?

  • Our vaccination campaign against smallpox worked because the vaccine was highly protective against infection, and smallpox had no close animal reservoir in which it could hide.


  • But SARS-CoV-2 can hide out in animals, and our current vaccines, while they provide excellent protection against severe illness and death, don't prevent all infections.

    しかし、SARS-CoV-2 は動物の体内に潜んでいることがあり、現在のワクチンは重症化や死亡を防ぐのに優れているものの、すべての感染を防げるわけではありません。

  • So, conceivably, there are two ways that SARS-CoV-2⏤the entire speciescould go extinct.


  • A cataclysmic disaster could kill us all, or we could invent a universal vaccine that prevents all SARS-CoV-2 infections,

    大災害が起これば私たち全員が死ぬかもしれないし、すべての SARS-CoV-2 感染を予防する万能ワクチンが発明されるかもしれないのです。

  • those caused by all the variants that currently exist and those that don't.


  • Let's work toward that second option.


  • If a universal vaccine for COVID sounds appealing, what about a vaccine that protects you against everything?

    COVID の万能ワクチンが魅力的に聞こえるなら、あらゆるものから身を守るワクチンはどうでしょう?

  • Learn more about the pitfalls and promise of a universal vaccine with this video, or watch this video to learn about some older pandemic technologyplague masks.


["An inefficient virus kills its host. A clever virus stays with it." - James Lovelock]

["非効率なウィルスは宿主を殺す。賢いウィルスは宿主と一緒にいる。" - ジェームズ・ラヴロック]

審査済み この字幕は審査済みです

ワンタップで英和辞典検索 単語をクリックすると、意味が表示されます

B1 中級 日本語


  • 29091 148
    shuting1215 に公開 2023 年 01 月 25 日